12-10-2005 22:51

Adam Richards

Re: pic: Vex 2 Speed Mesh Shifter

Awesome transmission. Lemme know when you can get the servo to shift it properly... I'll be trying to replicate your design then

12-10-2005 22:56

Matt Krass

Re: pic: Vex 2 Speed Mesh Shifter

Thanks....I'll keep you posted..

Also, before I get any more comments about the redundant gears I know, I put them in there on purpose to try and reduce load since I had the extra gears and shaft space anyways. They are plastic gears....

12-10-2005 23:08

Arefin Bari

Re: pic: Vex 2 Speed Mesh Shifter

I am going to try to explain this right. As the picture shows, the output shaft is the same one as the shaft where shifting takes place. So wouldn't the shaft move back and forth (since it is mesh shifting and you got a wheel on the same shaft). How is that going to affect the wheel on the output shaft?

From what I am looking at, my suggestion would be to add a pinion gear (bunch of vex gears together) to the shifting shaft (on the right side of the picture, you might have to make the width of the tranny a bit bigger), and then mesh it with another gear on a new shaft. Make the new (third) shaft the output shaft.

Matt, I know you are limited to one vex kit. This was just a suggestion. So far you have done a great job. I like the way it is coming out. Figure out how you are going to shift and you got yourself a sweet little mesh shifter. Can't wait to see what you come up with next. Good luck.

13-10-2005 01:19

Winged Globe

Re: pic: Vex 2 Speed Mesh Shifter

Very nice system. We also used a servo link when we built our prototype shifter for the spring Vex competition and it worked quite well. With only the starter kits, I think that's the way to go.

The material limit is definitely the hardest challenge. In order to accommodate the shaft movement, we vigorously ran a shaft through the center of an "output gear" to go on the shifting shaft. The gear was braced between the frame and another piece of metal. The shaft moved freely, and we didn't have any noticeable slipping of the gear. The output gear transmitted to a final wheel shaft on the exterior of the bot.

Why didn't it work? 1) We ended up needing all those gears for the arm, and we guessed that shifting would give marginal point benefit during the game. 2) We had a lot of shaft collars to make sure the gears didn't move, adding a lot of extra weight (though you may want to consider this if your gears get loose). 3) Plus, doing six-wheel drive by way of a nine gear gear train on each side in addition to the 3-speed shifter shot our turning efficiency to 0 (and again, no gears left). It worked wonderfully going straight, though... Haven't tried it with the sprocket and chain kit yet.

Can't wait to see your take on this (and with only 1 kit!).

13-10-2005 10:53

artdutra04

Re: pic: Vex 2 Speed Mesh Shifter

This is cool! I have a question though. Will this shifting gearbox be for a drive train application? If so, the way it is geared, it looks slow for a drive train. But it would make a killer arm gearbox.

13-10-2005 15:05

Michael Leicht

Re: pic: Vex 2 Speed Mesh Shifter

how are you going to keep the 2nd speed in gear?(with the servo and all)

what way do you have a shift so far?

nice design.

13-10-2005 19:13

Arefin Bari

Re: pic: Vex 2 Speed Mesh Shifter

As of right now (according to the pic), he doesn't shift the gears (you can, but only with your hand). He is working on making a piece that will help the shift shaft move back and forth, so it engages in different gears.

16-10-2005 20:30

skimoose

Re: pic: Vex 2 Speed Mesh Shifter

Very nice work! Let us know how the gears hold up to some wear and tear.

Why are Arefin and you talking of a one kit limit. Is that all you have to work with? If so, stock up gear kits are $12.99!

I just rechecked the 2005-2006 rules and there is no limit on hardware components for this year's competition. Rule R5a,b,&c only limit you to one vex controller, eight servos or motors (the controller's limit), one battery pack, two RF receivers, and a small amount of non-vex material (rubber bands, rope, velcro, and non-slip pad). No other vex components have limits, other than the sanity limit... Beware the 60 pound vex behemoth!

16-10-2005 21:04

JVN

Re: pic: Vex 2 Speed Mesh Shifter

It's actually pretty cool.
Vex is self-limiting in this regard. If you've got a 60 lb behemoth, you better stock up on motor clutches! Or... gear it at some super-slow speed.

(I wonder if you can even cram 60lbs worth of Vex into a 18x18x12 box?)

16-10-2005 21:13

Adam Richards

Re: pic: Vex 2 Speed Mesh Shifter

If you used a trash compactor you probably could

17-10-2005 20:58

skimoose

Re: pic: Vex 2 Speed Mesh Shifter

True. Vex motors are not very forgiving to over-design/over-building, but some teams will try and learn the hard way. How many threads were on the vexrobotics forum about stripping motor gears and broken clutches?
That's why the engineering notebook will come in handy. We usually learn more from our failures, than from our successes!